Method and apparatus for analyzing water concentration in a hydrocarbon sample by electrolysis



June 21, 1966 R. A. SANFORD ET A 3,257,609

METHOD AND APPARATUS FOR ANALYZING WATER CONCENTRATION IN A HYDROCARBON SAMPLE BY ELECTROLYSIS Original Filed Dec. 22, 1960 2| 26 I8 Z /Q I DETECTOR ELECTROLYTW COOLANT 23 INLET WATER ANALYZER 2 COLUMN PACMNG OF PMJETHYLENE GLYCOLS 8 POLYPROPYLENE GLYCOLS ON INERT SUPPORT TIMER CARRIER GAS II HYDROCARBON FEED IN V EN TORS R. A. SANFORD B.O. AYERS A 7' TORNE V5 United States Patent METHOD AND APPARATUS FOR ANALYZING WA'lER CONCENTRATION IN A HYDROCAR- BON SAMPLE BY ELECTROLYSIS Richard A. Sanford and Buell 0. Ayers, Bartlesville,

Okla, assignors to Phillips Petroleum Company, a corporation of Delaware Continuation of application Ser. No. 77,567, Dec. 22, 1960. This application Mar. 24, 1965, Ser. No. 444,932

11 Claims. (Cl. 324--30) This application is a continuation of application Serial No. 77,567, filed December 22, 1960, now abandoned.

This invention relates to an improved method of and apparatus for determining theconcentration of water in a hydrocarbon or mixture of hydrocarbons. In one specific aspect, this invention relates to an improved method of and apparatus for determining the concentration of water in a polymerizable hydrocarbon or a mixture of hydrocarbons, at least one of said hydrocarbons being polymerizable.

The art of removing water from hydrocarbon process streams is well known. Various analytical test methods have been utilized to determine the effectiveness ofwater separation processes and to otherwise determine the concentration of Water in a hydrocarbon or mixture of hydrocarbons. With processes requiring that the concentration of water, present as a trace, in a process hydrocarbon stream be accurately determined, it becomes necessary to employ an analytical method and apparatus capable of rapidly and accurately determining said water concentration. An apparatus capable of rapidly and accurately determining trace concentrations of water is described in US. 2,934,693.

When the water analyzer of the above patent, or other electrolytic water analyzers, are employed to determine the concentration of water in a butadiene stream, for example, butadiene polymerizes, thus reducing or entirely preventing the sample flow. Similar results are obtained in the analysis for the concentration of water in process streams containing other olefinic hydrocarbons. The reason for this is not entirely understood. However, for example, it is well known in the art that phosphoric acid catalysts are effective in promoting polymerization reactions. A phosphoric acid solution is employed in US. 2,934,693 to wet the electrodes of the sample cell; a current is passed to the electrodes to electrolyze the water from the phosphoric acid; nitrogen is passed to the cell to remove the oxygen and hydrogen, leaving a film of phosphorus pentoxide on the wires or electrodes to absorb the Water in the sample. By passing a sample containing an unsaturated olefinic hydrocarbon to the sample cell, polymerization of the unsaturated hydrocarbon occurs.

Accordingly, an object of this invention is to provide an improved method of and apparatus for determining the concentration of water in a hydrocarbon or mixture of hydrocarbons.

Another object of this invention is to provide an improved method of an apparatus for determining the concentration of water in a polymerizable hydrocarbon or mixture of hydrocarbons, at least one of said hydrocarbons being polymerizable.

Other objects, advantages, and features of our invention will be readily apparent to those skilled in the art from the following description and appended claims.

Broadly, we have discovered that water in a hydrocarbon or a mixture of hydrocarbons can be separated from said hydrocarbon or mixture of hydrocarbons by introducing said water-containing hydrocarbon or mixture of hydrocarbons into a chromatographic zone, said zone containing a stationary liquid selected from the group consisting of polyethylene and polypropylene glycols upon an inert support. A carrier gas can then be passed to the zone and a portion of the effluent from the chromatographic zone comprising said water can be passed to an electrolytic water analyzer wherein the water concentration of said efiluent is determined.

The drawing is a schematic diagram of the inventive process.

Referring to the drawing, there is shown a column 13 which is filled with a packing material that selectively retards the passage therethrough of the water vapor of the fluid mixture to be analyzed. The packing material comprises a stationary liquid selected from the group consisting of polyethylene and polypropylene glycols supported upon an inert material such as Chromosorb, a fire brick material manufactured by Johns-Manville to be used in chromatographic analyzers. The glycol selected is one that is normally liquid at operating temperatures and relatively involatile at the highest temperature to which column 13 is to be subjected. Examples of suitable polyethylene glycols are the polyethylene glycols 200, 300, 400 and 600 marketed by Union Carbide under the trademark of Carbowax. Examples of suitable polypropylene glycols are polypropylene glycols and 425 marketed by Union Carbide. The concentration of the stationary liquid on the inert packing material is preferably in the range 5-15 weight percent of the packing material.

A suitable method of combining the stationary liquid and the inert support is to dissolve the stationary liquid in a solvent such as methylene chloride. The prepared solution is then added to the inert support material. The resulting slurry is then dried under a heat lamp and reactivated under a vacuum for l-2 hours at a temperature slightly above the boiling point of the volatile solvent.

A fluid sample to be analyzed is introduced at a uniform controlled flow rate as a vapor to the inlet of column 13 by means of a conduit 10 and a three-way control valve 12. A carrier gas such as helium is introduced at a uniform controlled flow rate into the column 13 by means of a conduit 11 and control valve 12. The efliuent from column 13 is removed through a conduit 14 which communicates with the inlet of a three-way control valve 15. A portion of the sample to be analyzed is passed by means of a conduit 17 to the inlet of a detector 18. The re mainder of the sample is vented by means of a conduit 16. A conduit 19provides a means whereby the effluent from detector 18 is vented.

Detector 18 can be any electrolytic water analyzer known in the art that can be employed to accurately determine trace concentrations of water in the sample feed stream and to further determine concentrations of water up to and including 5.0 weight percent. Such a detector is described in US. 2,934,693 wherein the Water analyzer is described as comprising apparatus for the continuous adsorption and electrolyzing of the water present in the feed vapor. The current required to electrolyze the water is a direct function of the concentration of the water in the vapor.

Electrodes 23 and 24 provide a means whereby column 13 can be rapidly heated, said column 13 fabricated from a material having a lcfiv electrical conductivity. An electric voltage is passed to electrodes 23 and 24 by means of lead wires 21 and 22, respectively. A more detailed description of this method of heating a chromatographic column can be found in application Serial No. 40,339, by Gerald H. Overfield and assigned to Phillips Petroleum Company, filed September 28, 1960. Column 13 is also provided with a jacket 25 and means of introducing a cooling medium to said jacket through a conduit 26 and withdrawing said cooling medium through a conduit 27. A preferred cooling medium, but not necessarily limited thereto, is air supplied by a blower. It is, of course, within the scope of this invention to employ other methods of heating'and cooling column 13 than herein disclosed. Control valves 12 and are operated by a timer 20. This timer provides output signals that operate the valves in sequence and can be any type of apparatus known in the art providing control signals in a desired sequence. One common type of timer which can be employed utilizes a series of cam operated switches wherein associated cams are rotated by a timing motor. -It is, of course, within the scope of this invention to employ timer so as to control the flow of heat to column 13 and the cooling of column 13 in a desired sequence.

Referring again to the drawing, a hydrocarbon or a mixture of hydrocarbons, hereinafter referred to as a hydrocarbon sample feed, having a concentration of water of less than 5.0 weight percent is introduced into column 13 becomes saturated with the Water passed to inventive process can be employed to determine the concentration of water in any vaporizable hydrocarbon or mixtures of hydrocarbons, but it is particularly applicable to the determination of the concentration of water present in an unsaturated polymerizable olefinic hydrocar- =bon. The quantity of sample that can be passed to column 13 for any single water concentration determination is limited to the point at which the packing material of column 13 becomes saturated with the water passed to column 13 in the sample feed.

A carrier gas such as helium is then passed to column 13 via conduit 11 and control valve 12. A efiiuent hydrocarbon stream is first removed from column 13 via conduit 14 and vented via conduit 16 and three-way control valve 15. Column 13 is then, preferably, rapidly heated while continuing to pass said carrier gas to said column 13 and a substantially hydrocarbon-free vaporous stream is passed from column 13 via conduit 14, control valve 15 and conduit 17 to an electrolytic water analyzer 18. It is within the scope of this invention to eliminate the heating step and to remove the water from column 13 by passing said carrier gas through said column 13. Detector 18 measures a property of the efiiuent from column 13 which is representative of the concentration of water in the sample feed stream passed to column 13.

Column 13 is heated in the aforementioned manner so as to raise the temperature of the column in the range of 100-200 F. above an ambient or operating temperature of approximately 100 F the temperature of the column to be raised to its predetermined level within approximately 30 seconds. After the water vapor has passed fromcolumn 13, said column 13 is rapidly cooled to the ambient temperature by means of a cooling medium such as air passed to jacket by means of conduit 26 and removed via conduit 27. Column 13 is now prepared to receive the next sample.

It is necessary in the application of the inventive process that the time required to pass a substantially water-free hydrocarbon stream from column 13 be determined in order that control valve 15 can be set to operate in the desired sequence. This can be done, for example, by passing the efiiuent from column 13 to a thermal conductivity cell, not herein illustrated, thus determining the time required for the passage of the water-free hydrocarbon from column 13.

The following specific example is presented as illustrative of the inventive method of analysis.

Example Column 13 is formed of 2 feet of A-inch stainless steel tubing and containing 5 percent by weight, based on the packing material, of polyethylene glycol (Carbowax 1000) upon 100-140 mesh Chromosorb as an inert packing support. A vaporous butadiene sample is passed to column 13 at the rate of 65 cc./rnin. for a time period of 7 minutes. The efiiuent of the column is vented by means of conduit 16. The temperature of the column is 120 F. At this point helium is passed to the column at the rate of 65 cc./min. for a period of 1% minutes. The column is then heated so as to raise the temperature of the column to 250 F. within 30 seconds and at the same time valve 15 is changed so as to pass the column efliuent to water analyzer 18. After an additional period of 2 minutes the column is cooled by passing air through jacket 25 and valve 15 changed in preparation for the next sample. Electrolyzing the water in the efiluent passed to detector 18 indicates from a measurement of the current required to electrolyze said water that the butadiene sample stream contained p.p.m. of water.

As will be evident to those skilled in the art, various modifications of this invention can be made, or followed, in the light of the foregoing disclosure and discussion without departing from the spirit or scope thereof.

We claim:

1. A method which comprises introducing a vaporized hydrocarbon sample feed containing water into the inlet of a zone containing a material comprising a stationary liquid on an inert support packing, said stationary liquid consisting of a glycol selected from the group consisting of polyethylene glycols and polypropylene glycols, Withdrawing a substantially water-free hydrocarbon from said Zone, and thereafter withdrawing from said zone a substantially hydrocarbon-free water stream.

2. A method which comprises introducing a vaporized hydrocanbon sample feed containing water into the inlet of a zone containing a material comprising a stationary liquid on an inert support packing, said stationary liquid consisting of a glycol selected from the group consisting of polyethylene glycols and polypropylene glycols, passing a carrier gas to said zone, withdrawing a substantially water-free hydrocarbon and carrier gas stream from said zone, and thereafter withdrawing from said zone a substantially hydrocarbon-free water and carrier gas stream.

3. The method of claim 2 wherein said hydrocarbon is butadiene and said stationary liquid is polyethylene glycol.

4. The method of analyzing for the concentration of water in a hydrocarbon or a mixture of hydrocarbons which comprises introducing a vaporized hydrocarbon sample feed having a concentration of water of less than 5.0 weight percent into the inlet of a first zone which contains a material comprising a stationary liquid on an inert support packing, said stationary liquid consisting of a glycol selected from the group consisting of polyethylene glycols and polypropylene glycols, venting a substantially water-free hydrocarbon passed from said first zone, introducing a carrier gas into the inlet of said first zone, passing an efiluent from said first zone containing said water vapor into the inlet of a second zone, said second zone comprising a means of absorbing and electrolyzing said water vapor, and measuring the current employed to electrolyze said water vapor which is representative of the water concentration of said hydrocarbon sample feed.

5. The method of claim 4 wherein said hydrocarbon sample feed comprises, at least in part, an unsaturated olefinic hydrocarbon.

6. The method of claim 4 wherein the concentration of stationary liquid on the inert support packing is in the range of 5 to 15 weight percent of said material.

'7. The method of analyzing for the concentration of water in a hydrocarbon or a mixture of hydrocarbons which comprises introducing a vaporized hydrocarbon sample feed having a concentration of water of less than 5.0 weight percent into the inlet of a first zone containing a stationary liquid on an inert support packing, said stationary liquid consisting of a glycol selected from the group consisting of polyethylene glycols and polypropylene glycols, venting a substantially water-free efiluent withdrawn from said first zone, introducing a carrier gas into the inlet of said first zone, heating said first zone rapidly after the said venting step is complete, passing a substantially hydrocarbon-free efiluent from said first zone containing said water vapor into the inlet of a second zone, said second zone comprising a means of absorbing and electrolyzing said water vapor, and measuring the current employed to electrolyze said Water vapor which is representative of the Water concentration of said hydrocarbon sample feed.

8. The method of claim 7 wherein said first zone is heated so as to raise the temperature of said first zone in the range of 100-200 F. above the ambient temperature of said first zone.

9. Apparatus comprising, in combination, a column containing a packing material comprising a stationary liquid on an inert support, said stationary liquid consisting of a glycol selected from the group consisting of polyethylene glycols and polypropylene glycols, a first conduit inlet means communicating with said column at one end of said packing material, means of elect-rolyzing Water vapor, a second conduit means communicating between said column at the opposite end of said packing material and said means of electrolyzing said water vapor, a vent means communicating With said second conduit means upstream of said electrolyzing means, and a means of measuring the current employed to electrolyze said Water vapor.

1t). Apparatus comprising, in combination, a column containing a packing material that selectively retards passage therethrough of the Water vapor contained in a vaporized hydrocarbon sample feed, said packing material comprising a stationary liquid on an inert support, said stationary liquid consisting of a glycol selected from the group consisting of polyethylene glycols and polypropylene glycols, a means of heating said column, a first conduit inlet means communicating with said column at one end of said packing material, means of electrolyzing Water vapor, a second conduit means communicating between said column at the opposite end of said packing material and said means of electrolyzing said water vapor, a vent means communicating with said second conduit means upstream of said electrolyzing means, and a means of measuring the current employed to electrolyze said water vapor Which is representative of the Water concentration of said hydrocarbon sample feed.

11. The apparatus of claim 10 wherein there is supplied a means of cooling said column.

References Cited by the Examiner UNETED STATES PATENTS 4/1958 Keidel 3243O X 4/1960 Reinecke et al. 324- OTHER REFERENCES Carlstrom et al., Analytical Chemistry, volume 32, N0. 8, July 1960, page 1056 (received June 23, 1960). 

1. A METHOD WHICH COMPRISES INTRODUCING A VAPORIZED HYDROCARBON SAMPLE FEED CONTAINING WATER INTO THE INLET OF A ZONE CONTAINING A MATERIAL COMPRISING A STATIONARY LIQUID ON AN INERT SUPPORT PACKING, SAID STATIONARY LIQUID CONSISTING OF A GLYCOL SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE GLYCOLS AND POLYPROPYLENE GLYCOLS, WITHDRAWING A SUBSTANTIALLY WATER-FREE HYDROCARBON FROM SAID ZONE, AND THEREAFTER WITHDRAWING FROM SAID ZONE A SUBSTANTIALLY HYDROCARBON-FREE WATER STREAM. 